An emergency airlift was the only option for 1500 stranded residents in the flood-hit Queensland town of Bundaberg to escape fast-flowing waters believed capable of sweeping entire houses away on Monday night.

Hundreds of residents in the suburb of North Bundaberg were plucked from their roofs by three RACQ Careflight helicopters and two army Black Hawks.

The force of the flood – running at an estimated 70km/h – meant residents could not be reached by boat.

"The water is everywhere ... it's the worst flood on record," Bundaberg Mayor Mal Forman said.

There were more than 2000 homes underwater in Bundaberg – by far the worst-affected city – with thousands of residents bunkered down in schools and at the site of the town's new Agro-Trend showgrounds.

As the drama unfolded in the central Queensland sugar town, Brisbane recorded the state's fourth flood-related death – a three-year-old boy who died after he was hit by a falling tree in the city's north.

The toddler was with his family watching floodwaters rise at Gordon Park from the Kedron Brook bikeway when a large gum tree fell on them about 8.30am on Monday.

The little boy died of severe head injuries at the Royal Children's Hospital on Monday night.

His pregnant 34-year-old mother remains in a critical condition in hospital with several broken bones and severe head injuries after becoming trapped beneath the tree.

In other incidents, the body of a motorcyclist was pulled from Oxley Creek, south of Brisbane on Monday. He had been swept off a flooded bridge before horrified onlookers in Greenbank on Sunday night.

In Burnett Heads, near Bundaberg, an 81-year-old man died after falling off his yacht as he tried to secure it against wild weather on Sunday.

And a 27-year-old man, who is believed to have been disabled, was washed away on Sunday when he and his mother and step-father tried to cross a flooded creek near Gympie.

It is understood the man's step-father was rescued shortly after the car was swamped, but his mother was forced to cling to tree for more than four hours before she could be saved.

The skipper of a 12-metre boat off the coast of Rockhampton has been missing since Thursday.

Premier Campbell Newman has repeatedly assured Brisbane and Ipswich residents the floods will be nothing like those two years ago that swept across Queensland, killing 35 people and leaving a $6 billion reconstruction task.

But, for many, the memories are too raw.

Louise Toohey, whose home was inundated two years ago, was among anxious residents evacuating homes on Monday.

Ferocious seas on the Gold Coast sent waves crashing through the windows of waterfront restaurants, and whipped up foam that blanketed roads.

Regional centres across central and southern Queensland, including Gladstone, Gympie, Maryborough, Warwick, Laidley and Rockhampton, have flooded, with the town of Condamine, west of Chinchilla, facing a 12-metre river peak on Thursday or Friday.

West of Brisbane, in the Lockyer Valley, where flash flooding claimed 19 lives in 2011, more than 100 people stayed overnight in an evacuation centre at the local school.

Hundreds of schools across Queensland will remain closed for the beginning of the new school year, and Brisbane is bracing for commuter chaos on Tuesday with central rail lines damaged.

As ex-cyclone Oswald moved south overnight, about 2000 people were cut off by floodwaters in northern New South Wales, where heavy rain and winds of up to 140km/h battered the region.

The state government on Monday opened up disaster assistance funding to residents of 10 more Queensland regions, including those in Brisbane and Ipswich.

The Insurance Council of Australia said $43 million worth of insurance claims had already been lodged.

Prime Minister Julia Gillard said the crisis in Queensland was "breaking hearts".

"Across Queensland the wild weather has broken a lot of hearts. It's a very tough period," she said.

Queensland Premier Campbell Newman said the state would rise to the challenge.